This invention relates to neutron detection.
Neutron-sensitive microchannel plates (MCP) can be used to detect special nuclear materials (SNM), such as plutonium, or can be used as highly effective detectors in neutron imaging or neutron diffraction. A microchannel plate can be formed by bonding a glass plate between an input electrode and an output electrode, and providing a high voltage direct current (DC) field between the electrodes. The glass plate is perforated with a substantially regular, parallel array of microscopic channels, for example, cylindrical and hollow channels. Each channel, which can serve as an independent electron multiplier, has an inner wall surface formed of a semi-conductive and electron emissive layer.
The glass plate can be doped with, for example, boron-10, which can capture neutrons in reactions that generate lithium-7 and alpha particles. As the lithium-7 and alpha particles enter nearby channels and collide against the wall surfaces to produce secondary electrons, a cascade of electrons can be formed as the secondary electrons accelerate along the channels (due to the DC field), and collide against the wall surfaces farther along the channels, thereby increasing the number of secondary electrons. Alternatively, although having a smaller neutron capture cross-section, the glass plate can be doped with lithium-6, resulting in triton and alpha particle reaction products which likewise produce a cascade of electrons. The electron cascades develop along the channels and are amplified into detectable signals that are electronically registered and processed to construct a digital image. The resultant intensity map or image corresponds to the variation in neutron flux striking the microchannel plate surface. Contrast differences within the image of a sample can be used to infer physical and chemical properties.